When Huan first met the man named Karashima Haruka, he honestly wasn't sure whether they would get along with each other. Sure he greeted the man normally, with his usual bright and cheerful smile. But Huan wasn't that naive. When he first met Haruka, the guy was dragging his feet away from a fight - and even after Haruka retreated. Those people went after him. Huan remembers being in the park that day complaining about how they gave him too much food when he ordered. Even if he liked burgers, there was no way he could eat so much. So when Huan saw Haruka in a pinch he thought, 'perfect, somebody to give my burgers too.'
When Huan saved Haruka, he didn't even know it was him, until after the fight. When Huan finally recognized the guy who he saved.